Internally-cooled centrifugal compressor with cooling jacket formed in the diaphragm

ABSTRACT

An internally-cooled centrifugal compressor having a shaped casing and a diaphragm disposed within the shaped casing having a gas side and a coolant side so that heat from a gas flowing through the gas side is extracted via the coolant side. An impeller disposed within the diaphragm has a stage inlet on one side and a stage outlet for delivering a pressurized gas to a downstream connection. The coolant side of the diaphragm includes at least one passageway for directing a coolant in a substantially counter-flow direction from the flow of gas through the gas side.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/930,751, which was filed on Jan. 14, 2011, which claims priority toU.S. Provisional Patent Application Ser. No. 61/402,983, which was filedon Sep. 9, 2010, the disclosures of which are incorporated herein byreference to the extent consistent with the present application.

STATEMENT OF GOVERNMENT INTEREST

This invention was made with government support under GovernmentContract No. DE-FC26-05NT42650 awarded by the U.S. Department of Energy.The government has certain rights in the invention.

TECHNICAL FIELD

Embodiments of the disclosure are generally related to systems forisothermal compression. Specific embodiments of the disclosure relate toan internally-cooled centrifugal compressor with greatly increased heattransfer properties. A more specific embodiment of the disclosurerelates to a compressor utilizing a cooled diaphragm section withinternal cooling passages through the diffuser and return channel vanessuch that cooling flows in a substantially counter-flow direction of gasflow.

BACKGROUND OF THE DISCLOSURE

Compressors are well known in the art with their primary function beingto increase the pressure of a gas. It is also well known thatcompression of a gas not only increases pressure, but also causesheating of the gas by the work of compression. Thus, a gas isconsiderably hotter at the discharge than at the inlet of thecompressor. In multistage compressors, for subsequent stages, thisincrease in heat (or temperature) requires greater heat rise for a givenpressure ratio, which requires more power than compressing a cool gas.

Isothermal compression has been used as a way of maintaining a constanttemperature during the gas compression process which, in turn, reducesthe compression power required. However, typical isothermal compressionprocesses will compress the gas in steps with intercooling between thesesteps with the downside of increased complexity and size of thecompressor apparatus.

Thus, a need exists for an efficient means of compressing a gas thatmaximizes heat transfer while also minimizing aerodynamic pressurelosses. A means of achieving isothermal compression of a gas without thesize and piping requirements of prior art isothermal compressors wouldprovide numerous advantages.

SUMMARY OF THE DISCLOSURE

The following summary is provided to facilitate an understanding of someof the innovative features unique to the present disclosure and is notintended to be a full description. A full appreciation of the variousaspects of the embodiments disclosed herein can be gained by taking theentire specification, claims, drawings, and abstract as a whole.

It is, therefore, one aspect of the present disclosure to provide for animproved compressor apparatus. It is another aspect of the presentdisclosure to provide for an internally-cooled compressor that allowsisothermal compression of a gas. It is a further aspect of the presentdisclosure to provide for an improved isothermal compressor thatmaximizes heat transfer while not introducing additional aerodynamiclosses in the gas flow path. It should be noted that the term“isothermal” also includes operation at a semi-isothermal capacity,without departing from the scope of the disclosure.

The aforementioned aspects and other objectives and advantages can nowbe achieved as described herein. Briefly, disclosed is an isothermalcompressor with a cooling jacket structure formed in the diaphragm ofthe compressor. With the isothermal compressor of the presentdisclosure, cooling flow is routed through both the diffuser and returnchannel vanes and the bulb section of the diaphragm as a working fluidor gas is compressed through the diffuser and return channel. In oneembodiment, heat transfer is achieved using diffuser vanes with internalcooling holes through which the cooling flow is channeled. The vanesalso serve to increase pressure recovery in the diffuser. The returnchannel vanes may also define cooling holes that feed cooling flow intoa hollow plenum arranged inside the center bulb. As the gas passes bythe cooling flow coursing through the cooling holes of both the diffuserand return channel vanes and the center bulb, heat is extracted from theworking fluid without additional drop in pressure for the gas.

In one embodiment, the walls for the gas flow path are maintained smoothwhile the flow path for the cooling fluid is roughened in order tomaximize turbulence and heat transfer. Accordingly, in at least oneembodiment, all of the cooling holes defined within the diffuser andreturn channel vanes may be roughened to increase heat transfer. Surfaceroughness may be achieved by tapping a screw thread in each hole.

According to still another embodiment, an isothermal compressor isdisclosed that has an internally-cooled diaphragm with large structuralvanes that increase the strength of the diaphragm and also increase theturbulence of cooling liquid flow resulting in improved heat transfer.

Embodiments of the disclosure generally provide an internally-cooledcentrifugal compressor. The compressor may include a shaped casinghaving a stage inlet for an upstream gas connection and a stage outletfor a downstream gas connection, and a diaphragm arranged within saidshaped casing and having a gas side and a coolant side so that heat froma gas flowing through the gas side is extracted via said coolant side,wherein, the coolant side includes a cooling agent flow path fordirecting a cooling agent in a substantially counter-flow direction froma flow of the gas through the gas side.

Embodiments of the disclosure may further provide an internally-cooledcentrifugal compressor diaphragm. The compressor may include a rotatableimpeller centrally-disposed within the diaphragm, a diffuser fluidlycoupled to an outlet of the impeller and having a plurality of diffuservanes arranged therein, each diffuser vane having at least one diffuserconduit defined therein, and a return channel fluidly coupled to thediffuser and having a plurality of return channel vanes arrangedtherein, each return channel vane having at least one return conduitdefined therein. The compressor may further include a cooling jacketproximally-located about the diffuser and the return channel, thecooling jacket having a first chamber and a second chamber, and a centerbulb defined within the diaphragm and interposed between the diffuserand the return channel, the center bulb being in fluid communicationwith the first chamber via the at least one return conduit and in fluidcommunication with the second chamber via the at least one diffuserconduit.

Embodiments of the disclosure may further provide a method of cooling aworking fluid in a centrifugal compressor. The method may includecirculating the working fluid through a diffuser having a plurality ofdiffuser vanes arranged therein, each diffuser vane having at least onediffuser conduit defined therein, receiving the working fluid in areturn channel fluidly coupled to the diffuser and having a plurality ofreturn channel vanes arranged therein, each return channel vane havingat least one return conduit defined therein, circulating a cooling agentfrom a first chamber into a center bulb interposed between the diffuserand the return channel, the first chamber being located adjacent thereturn channel and in fluid communication with the center bulb via theat least one return conduit, and circulating the cooling agent from thecenter bulb to a second chamber, the second chamber being locatedadjacent the diffuser and in fluid communication with the center bulbvia the at least one diffuser conduit, whereby as the cooling agent iscirculated it removes heat from the working fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, in which like reference numerals refer toidentical or functionally-similar elements throughout the separate viewsand which are incorporated in and form a part of the specification,further illustrate the present disclosure and, together with thedetailed description of the disclosure, serve to explain the principlesof the present disclosure.

FIG. 1 is a cross-section view of a centrifugal compressor with aninternally-cooled diaphragm according to one embodiment.

FIGS. 2 a and 2 b are cross-section close up views of theinternally-cooled diaphragm in accordance with an embodiment.

FIG. 3 illustrates the domain of the cooling flow in accordance with anembodiment.

FIG. 4 is a close up view showing roughness in cooling holes.

FIG. 5 is a representative picture of an internally-cooled diaphragmaccording to one embodiment.

FIG. 6 is a schematic of a method of cooling a gas or working fluidbeing compressed in a centrifugal compressor.

DETAILED DESCRIPTION

It is to be understood that the following disclosure describes severalexemplary embodiments for implementing different features, structures,or functions of the invention. Exemplary embodiments of components,arrangements, and configurations are described below to simplify thepresent disclosure; however, these exemplary embodiments are providedmerely as examples and are not intended to limit the scope of theinvention. Additionally, the present disclosure may repeat referencenumerals and/or letters in the various exemplary embodiments and acrossthe Figures provided herein. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various exemplary embodiments and/or configurationsdiscussed in the various Figures. Moreover, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed interposing the first and second features, suchthat the first and second features may not be in direct contact.Finally, the exemplary embodiments presented below may be combined inany combination of ways, i.e., any element from one exemplary embodimentmay be used in any other exemplary embodiment, without departing fromthe scope of the disclosure.

Additionally, certain terms are used throughout the followingdescription and claims to refer to particular components. As one skilledin the art will appreciate, various entities may refer to the samecomponent by different names, and as such, the naming convention for theelements described herein is not intended to limit the scope of theinvention, unless otherwise specifically defined herein. Further, thenaming convention used herein is not intended to distinguish betweencomponents that differ in name but not function. Additionally, in thefollowing discussion and in the claims, the terms “including” and“comprising” are used in an open-ended fashion, and thus should beinterpreted to mean “including, but not limited to.” All numericalvalues in this disclosure may be exact or approximate values unlessotherwise specifically stated. Accordingly, various embodiments of thedisclosure may deviate from the numbers, values, and ranges disclosedherein without departing from the intended scope. Furthermore, as it isused in the claims or specification, the term “or” is intended toencompass both exclusive and inclusive cases, i.e., “A or B” is intendedto be synonymous with “at least one of A and B,” unless otherwiseexpressly specified herein.

Referring to FIG. 1, a cross-sectional view of a centrifugal compressoraccording to one or more embodiments is shown and denoted generally as10. The compressor 10 may be used to compress a gas or working fluid.Although the compressor 10 is shown with only one stage, it willappreciated that the compressor 10 can be utilized in a multi-stageconfiguration where substantially similar compressor stages are coupledtogether axially with each stage providing a cooler gas to a subsequentdownstream stage.

There are many applications for the use of a centrifugal compressor 10such as, for example, the compression of CO₂ associated with carboncapture and sequestration projects and other similar attempts to reduceemissions while conserving energy. As will be described herein, thecompressor 10 provides significant reduction in the required powerassociated with compression of all gases, including CO₂, by performingnear or at isothermal compression. Accordingly, the compressor 10 mayreduce the need for intercoolers or eliminate the need for intercoolersaltogether.

In exemplary operation, the gas travels through the compressor 10generally in the direction of arrow 20 from a stage inlet 22 to a stageoutlet 24. The stage inlet 22 provides a pipe connection from a sourceof gas to a housing or shaped casing 26 containing the variouscompressor components. Likewise, stage outlet 24 provides a pipeconnection to a downstream system for receiving the pressurized gas. Thecompressor 10 includes a rotating impeller 28 arranged within the shapedcasing 26 and configured to force the gas to the tip 30 of the impeller28, thereby increasing the velocity of the gas entering the diffuser 34.A diaphragm section (or “diaphragm” as the terms shall be usedinterchangeably) 32 includes all of the various components containedwithin the back half or downstream end of the shaped casing 26 and formsthe gas flow path of compressor 10. In particular, the diaphragm 32includes a diffuser 34 fluidly coupled to a return channel 48. Thediffuser 34 is configured to convert the velocity energy of the gasreceived from the impeller 28 to pressure energy, resulting in thecompression of the gas. The return channel 48 is configured to receivethe compressed gas from the diffuser 34 and eject the compressed gasfrom the gas flow path via the stage outlet 24, or otherwise inject thecompressed gas into a succeeding compressor stage (not shown).

Referring now to FIGS. 2 a and 2 b, the diaphragm 32 includes aplurality of diffuser vanes 42 are arranged within the diffuser 34, anda plurality of return channel vanes 66 are arranged within the returnchannel 48. Moreover, the diaphragm 32 encompasses both a gas side and acoolant side. As illustrated in FIG. 2 a, the gas side may generallyrefer to or include the gas passageway defined by a combination of thediffuser 34 and the return channel 48. On the other hand, the coolantside may generally include a cooling jacket 46 proximally-located aboutor otherwise surrounding the gas side (i.e., adjacent both the diffuser34 and the return channel 48). As will be described in more detail belowwith reference to FIG. 2 b, the coolant side may further include acenter bulb 68. The cooling jacket 46 forms a barrier through which acooling agent can flow for extracting heat from the pressurized gasflowing through the diffuser 34 and the return channel 48. According tothe disclosure, the fact that the cooling jacket 46 is contained withinthe diaphragm 32 of the compressor 10 provides an efficient way ofextracting heat from the pressurized gas flowing in the gas side.

As shown in FIG. 2 b, the cooling agent may be configured to follow aflow path represented by arrow 60, which generally follows asubstantially counter-flow path in a direction similar to, for example,a counter-flow heat exchanger. In particular, the cooling agent flowdirection 60 may be substantially opposite that of the gas flowdirection 20. In one embodiment, the cooling agent flow path 60 mayoriginate in a first or right chamber 62 defined by the cooling jacket46. From the right chamber 62, the cooling agent may be fed through oneor more return conduits 64 defined or otherwise formed in the returnchannel vanes 66 of the return channel 48. The return conduits 64 mayfeed the cooling agent into a center bulb 68 defined by the diaphragm32. The center bulb 68 may include a plenum adapted to feed the coolingagent into one or more diffuser conduits 70 defined or otherwise formedin the diffuser vanes 42 (see FIG. 2 b). The cooling agent is ultimatelygathered in a second or left chamber 80 defined by the cooling jacket46. From the left chamber 80, the cooling agent exits the compressor 10to be eventually recirculated back to the right chamber 62 in order tostart the cooling agent flow path over again.

In one or more embodiments, the cooling agent may include a coolant,such as ambient water, chilled water or ethylene glycol. It will beappreciated, however, that the cooling agent is not limited to liquidsonly, as gases could also be used as a suitable coolant source. In oneembodiment, the cooling agent exiting the left chamber 80 may becirculated through one or more heat exchangers before being reintroducedin the right chamber 62.

Referring now to FIG. 3, the domain in which the cooling agent is madeto flow is shown and denoted generally as 100. As illustrated, the rightchamber 62 is fluidly coupled to the left chamber 80 via a network ofreturn and diffuser conduits 64, 70 and the center bulb 68.

It has been found that maximizing the surface area of the cooling domain100 provides the most efficient transfer of heat from the pressurizedgas flowing in the gas side to the cooling agent flowing in the coolantside. Consequently, the surface area of the cooling domain 100 ismaximized through the implementation of return conduits 64 and diffuserconduits 70 within the return channel vanes 66 and diffuser vanes 42,respectively. In this way, an internal means of heat extraction isprovided to a single stage or multi-stage compressor apparatus, such asthe compressor 10 described herein.

It should be understood that the present disclosure is not limited to aparticular configuration of diaphragm, such as the diaphragm 32described herein. Instead, the current disclosure encompasses unique andnovel aspects relating to the efficient operation of a compressor, suchas compressor 10, where internal cooling is provided by maximizing thesurface area of the cooling domain side of the diaphragm section 32inside the compressor 10 without negatively impacting gas pressure.Thus, Applicants of the present disclosure have discovered that variousfeatures can be utilized within the diaphragm section 32 to improveefficiency and avoid negative impacts on compressor 10 performance.

One such feature involves the physical aspects of the diaphragm section32. For example, it has been discovered by Applicants that maintainingthe gas flow path within a substantially smooth-walled structure whiledirecting the cooling agent through a cooling agent flow path having aroughened-walled structure maximizes turbulence in the coolant side andheat transfer while keeping pressure drop on the gas side identical to astandard (non-cooled) compressor design. As used herein, a“smooth-walled structure” generally refers to a diaphragm 32 that hasnot been intentionally roughened, i.e., does not create significantturbulence with the gas/fluid flowing thereby, so as to result in adiaphragm 32 having walls that are coarse, jagged, or rugged. Moreover,as used herein, a “roughened-walled structure” includes, but is notlimited to, threading the return and diffuser conduits 64, 70 so as togenerate coarsely threaded holes that make a tortuous flow path for thecooling agent flowing therethrough. The term “roughened-walledstructure” may also include or otherwise refer to the implementation oraddition of structural vanes 160 within the coolant side of thediaphragm 32, as will be described in more detail below with referenceto FIG. 5.

The diaphragm 32, including the cooling jacket 46, center bulb 68,diffuser vanes 42, and return channel vanes 66, may be manufactured viaa variety of manufacturing processes. For example, in one manufacturingprocess the diaphragm 32 is fabricated by first machining the individualcomponents, such as by computer numerically controlled (CNC) millingtechniques. The machined pieces may then be welded together, heattreated, and then final-machined to smooth each weldment. Because of thecomplexity of the diaphragm 32 and its components, the diaphragm 32 maybe machined and welded throughout multiple stages. For instance, thebulb 68 pieces may be machined in two sections; one section containingthe diffuser vanes 42, and the other section containing the returnchannel vanes 66. These two sections can be welded together to completethe bulb section 68. Moreover, the main structural sections of thecooling jacket 46 may also be machined using two pieces for each half;one piece for the diffuser vane side and another for the return channelside. These two sections may be welded to the bulb section 68 at boththe diffuser and return channel vanes 42, 66 and may then be welded toeach other at the perimeter.

It will be appreciated, however, that other forms of manufacturing maybe employed, without departing from the scope of the disclosure. Forexample, it is also contemplated herein to cast the diaphragm 32 as asingle component, such as by sand casting, plaster mold casting,investment casting, or die casting.

Referring to FIG. 4, illustrated is a portion of the coolant side of thediaphragm 32 showing a plurality of diffuser conduits 70 having coarselydrawn threads defined therein. It will be appreciated that the diffuserconduits 70 shown in FIG. 4 may equally be depicted as return conduits64 which are substantially similar, but not necessarily geometricallyidentical, to the diffuser conduits 70. The use of coarsely threadedholes increases the turbulence of the cooling agent flowing therein andalso increases the surface area of each conduit 64 or 70. Consequently,the overall heat transfer from the gas in the gas side to the coolantside is enhanced. In at least one embodiment, threading the conduits 64or 70 may also prove advantageous by simplifying the manufacturingprocess as compared to other turbulence generators.

FIG. 5 is a pictorial representation of one half of an exemplarydiaphragm 32 showing a portion of the inside of the cooling jacket 46.Also illustrated is a plurality of diffuser conduits 70. It will beappreciated that the diffuser conduits 70 shown in FIG. 5 may equally bedepicted as return conduits 64 which, as described above, aresubstantially similar, but not necessarily geometrically identical, tothe diffuser conduits 70. In an embodiment, the cooling jacket 46 mayinclude one or more large structural vanes 160 that may be used to bothincrease the strength of the diaphragm 32 and also increase theturbulence of the cooling agent flowing therein, thereby increasing theheat transfer in this region. In operation, the structural vanes 160 mayminimize the shearing of the diaphragm 32 under pressure loading and maybe positioned so as not to interfere with the slot welding of thediffuser vanes 42 (or return channel vanes 66, in the event returnconduits 64 are shown). While only six structural vanes 160 are shown,it will be appreciated that any number of structural vanes 160 may beused, without departing from the scope of the disclosure.

Referring now to FIG. 6, illustrated is a schematic of a method 600 ofcooling a gas or a working fluid being compressed in a centrifugalcompressor. The method 600 may include circulating the working fluidthrough a diffuser, as at 602. In one embodiment, the diffuser has aplurality of diffuser vanes arranged therein, and each diffuser vane hasat least one diffuser conduit defined therein for the circulation of acooling agent. The working fluid may be received in a return channel, asat 604. The return channel may be fluidly coupled to the diffuser andhave a plurality of return channel vanes arranged therein. Similar tothe diffuser vanes, each return channel vane may have at least onereturn conduit defined therein for the circulation of the cooling agent.

A cooling agent may then be circulated from a first chamber into acenter bulb, as at 606. The center bulb may be interposed between thediffuser and the return channel, and the first chamber may be adjacentto or otherwise surrounding the return channel on at least one sidethereof. Moreover, the first chamber may be in fluid communication withthe center bulb via the return conduits defined within the returnchannel vanes. The cooling agent may further be circulated from thecenter bulb to a second chamber, as at 608. The second chamber may belocated adjacent to or otherwise surrounding the diffuser on at leastone side thereof. Furthermore, the second chamber may be in fluidcommunication with the center bulb via the diffuser conduits definedwithin the diffuser vanes.

Accordingly, as the cooling agent is circulated from the first chamberto the center bulb, and from the center bulb to the second chamber, heatis constantly being transferred from the working fluid to the coolingagent, thereby resulting in the overall cooling of the working fluid. Aswill be appreciated, the heat transfer may occur within the return vanesor diffuser vanes as the cooling agent passes therethrough, but may alsooccur within the first and second chambers as heat is passed from thereturn channel and diffuser into the first and second chambers,respectively. Moreover, heat transfer may occur in the cooling agentflowing in the center bulb.

The foregoing has outlined features of several embodiments so that thoseskilled in the art may better understand the present disclosure. Thoseskilled in the art should appreciate that they may readily use thepresent disclosure as a basis for designing or modifying other processesand structures for carrying out the same purposes and/or achieving thesame advantages of the embodiments introduced herein. Those skilled inthe art should also realize that such equivalent constructions do notdepart from the spirit and scope of the present disclosure, and thatthey may make various changes, substitutions and alterations hereinwithout departing from the spirit and scope of the present disclosure.

We claim:
 1. An internally-cooled centrifugal compressor, comprising: ashaped casing having a stage inlet for an upstream gas connection and astage outlet for a downstream gas connection; and a diaphragm arrangedwithin said shaped casing and having a gas side and a coolant side sothat heat from a gas flowing through the gas side is extracted via saidcoolant side, wherein the coolant side includes a cooling agent flowpath for directing a cooling agent in a substantially counter-flowdirection from a flow of the gas through the gas side.
 2. The compressorof claim 1, further comprising an impeller disposed within saiddiaphragm, the impeller having a first side fluidly coupled to the stageinlet for receiving the gas from the upstream gas connection anddelivering the gas to said impeller, and a second side fluidly coupledto said stage outlet for delivering a pressurized gas to the downstreamgas connection through said stage outlet.
 3. The compressor of claim 1,wherein the gas side of the diaphragm comprises: a diffuser having aplurality of diffuser vanes arranged therein, the diffuser beingproximally located near the coolant side of the diaphragm so that heatin the gas can be extracted by the cooling agent flowing through saidcoolant side; and a return channel fluidly coupled to the diffuser andhaving a plurality of return channel vanes arranged therein, the returnchannel being configured to deliver the pressurized gas to the stageoutlet of the diaphragm.
 4. The compressor of claim 3, wherein thecoolant side of the diaphragm comprises: a first chamber from which thecooling agent originates; a center bulb defined by the diaphragm andinterposed between the diffuser and the return channel, the center bulbbeing in fluid communication with the first chamber via one or morereturn conduits defined within the plurality of return channel vanes,wherein the cooling agent flows from the first chamber into the centerbulb; and a second chamber in fluid communication with the center bulbvia one or more diffuser conduits defined within the plurality ofdiffuser vanes, wherein the cooling agent flows from the center bulbinto the second chamber.
 5. The compressor of claim 4, wherein thereturn conduits and/or the diffuser conduits are coarsely threaded. 6.The compressor of claim 4, wherein the first chamber and/or the secondchamber of the coolant side is formed of a roughened-walled structure.7. The compressor of claim 4, wherein said gas side of said diaphragm isformed of a smooth-walled structure.
 8. The compressor of claim 4,wherein the first chamber and/or the second chamber have a plurality ofstructural vanes arranged therein to generate turbulence of the coolingagent.
 9. The compressor of claim 1, wherein the cooling agent is aliquid coolant.
 10. The compressor of claim 1, wherein the cooling agentis a gas coolant.
 11. An internally-cooled centrifugal compressordiaphragm, comprising: a rotatable impeller centrally-disposed withinthe diaphragm; a diffuser fluidly coupled to an outlet of the impellerand having a plurality of diffuser vanes arranged therein, each diffuservane having at least one diffuser conduit defined therein; a returnchannel fluidly coupled to the diffuser and having a plurality of returnchannel vanes arranged therein, each return channel vane having at leastone return conduit defined therein; a cooling jacket proximally-locatedabout the diffuser and the return channel, the cooling jacket having afirst chamber and a second chamber; and a center bulb defined within thediaphragm and interposed between the diffuser and the return channel,the center bulb being in fluid communication with the first chamber viathe at least one return conduit and in fluid communication with thesecond chamber via the at least one diffuser conduit.
 12. The diaphragmof claim 11, wherein the return conduits and/or the diffuser conduitsare coarsely threaded.
 13. The diaphragm of claim 11, wherein the firstchamber and/or the second chamber have a plurality of structural vanesarranged therein.
 14. The diaphragm of claim 13, wherein the structuralvanes provide structural support for the diaphragm.
 15. The diaphragm ofclaim 13, wherein the structural vanes introduce turbulence to a coolingagent flowing therein.
 16. The diaphragm of claim 11, wherein thediffuser and the return channel are smooth-walled structures.
 17. Amethod of cooling a working fluid in a centrifugal compressor,comprising: circulating the working fluid through a diffuser having aplurality of diffuser vanes arranged therein, each diffuser vane havingat least one diffuser conduit defined therein; receiving the workingfluid in a return channel fluidly coupled to the diffuser and having aplurality of return channel vanes arranged therein, each return channelvane having at least one return conduit defined therein; circulating acooling agent from a first chamber into a center bulb interposed betweenthe diffuser and the return channel, the first chamber being locatedadjacent the return channel and in fluid communication with the centerbulb via the at least one return conduit; and circulating the coolingagent from the center bulb to a second chamber, the second chamber beinglocated adjacent the diffuser and in fluid communication with the centerbulb via the at least one diffuser conduit, whereby as the cooling agentis circulated it removes heat from the working fluid.
 18. The method ofclaim 17, further comprising generating a turbulent cooling agent bycirculating the cooling agent within the first and second chambershaving structural vanes arranged therein.
 19. The method of claim 17,further comprising generating a turbulent cooling agent by circulatingthe cooling agent through a coarsely threaded return conduit and/or acoarsely threaded diffuser conduit.
 20. The method of claim 17, furthercomprising circulating the cooling agent through the first chamber, thecenter bulb, and the second chamber in a substantially counter-flowdirection with respect to a flow of the working fluid.